title: Comparative secretome analysis of four isogenic Bacillus clausii probiotic strains.
abstract: BACKGROUND
  The spore-bearing alkaliphilic Bacillus species constitute a large, heterogeneous group of microorganisms, important for their ability to produce enzymes, antibodies and metabolites of potential medical use. Some Bacillus species are currently being used for manufacturing probiotic products consisting of bacterial spores, exhibiting specific features (colonization, immune-stimulation and antimicrobial activity) that can account for their claimed probiotic properties. In the present work a comparative proteomic study was performed aimed at characterizing the secretome of four closely related isogenic O/C, SIN, N/R and T B. clausii strains, already marketed in a pharmaceutical mixture as probiotics.
  
  
  RESULTS
  Proteomic analyses revealed a high degree of concordance among the four secretomes, although some proteins exhibited considerable variations in their expression level in the four strains. Among these, some proteins with documented activity in the interaction with host cells were identified, such as the glycolytic enzyme enolase, with a putative plasminogen-binding activity, GroEL, a molecular chaperone shown to be able to bind to mucin, and flagellin protein, a structural flagella protein and a putative immunomodulation agent.
  
  
  CONCLUSIONS
  This study shows, for the first time, differences in the secretome of the OC, SIN, NR and T B. clausii strains. These differences indicate that specific secretome features characterize each of the four strains despite their genotypic similarity. This could confer to the B. clausii strains specific probiotic functions associated with the differentially expressed proteins and indicate that they can cooperate as probiotics as the secretome components of each strain could contribute to the overall activity of a mixed probiotic preparation.
authors.affiliation: Institute of Biomembranes and Bioenergetics, Italian National Research Council (CNR), Via Amendola 165/A, Bari, Italy. r.lippolis@ibbe.cnr.it.
authors.forename: Rosa
authors.initials: R
authors.lastname: Lippolis
authors.forename: Rosa Anna
authors.initials: RA
authors.lastname: Siciliano
authors.forename: Maria Fiorella
authors.initials: MF
authors.lastname: Mazzeo
authors.forename: Anna
authors.initials: A
authors.lastname: Abbrescia
authors.forename: Antonio
authors.initials: A
authors.lastname: Gnoni
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Sardanelli
authors.forename: Sergio
authors.initials: S
authors.lastname: Papa